Phase modulation system



sept. 17, 1945.

PHASE MODULATION SYSTEI E. LABIN 2,407,887

.ATTRMEY Sept. 17, 1946. E. LABIN 2,407,887 PHASE MonLATIoN SYSTEM Filed latch 29,1944 3 Sheets-Sheet 2 /NvENv-oe: EoouA ED `LAB/ml,

Arras/EY lBY Patented Sept. 17, 1946 PHASE MoDULA'rIoN SYSTEM Edouard Labin, Buenos Aires, Argentina, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application March 20, 1944, Serial No. 527,286

Claims. (Cl. 179-1715) This invention relates to wave length modulation systems and more particularly to a system wherein the phase angle of a high-frequency oscillation is proportional to the amplitude of a modulating potential over a wide range of phase angle deviations.

In one type oi prior phase modulation systems, the phase modulated oscillation is generated by vectorially combining .the constant amplitude carrier wave with the side-bands whose amplitudes are linearly modulated in phase opposition. The main drawback oi these systems is that a linear relation between the amplitude of the modulating intelligence and the resultant phase of the modulated oscillation can solely be maintained for phase angle deviations which do not exceed $30". Furthermore, the modulation procedure also introduces a certain amount of amplitude modulation, so that amplitude limiter stages have to be used to obtain a pure phase modulated carrier oscillation.

In another type of known phase modulation systems wherein the resultant phase modulated oscillation is obtained by vectorially adding two linearly push-pull amplitude modulated oscillations having a phase difference smaller than vr, the resultant phase angle is proportional to the modulating potential 4for small deviation angles only, so that a wide band phase modulation is still accompanied by relatively large Variations in the amplitude of the modulated oscillation.

Leon Rubin has shown in the phase modulation system disclosed in U. S. patent application Serial No. 515,446 that by vectorially combining two non-linearly amplitude modulated oscillations of equal frequency having `some optimum phase difference smaller than 1r, the phase angle of the resultant oscillation will be substantially proportional to the amplitude of the modulating potential for phase angle variations not higher than 60 and that within this range the amplitude of the phase modulated oscillation will remain practically constant.

I have now found that if the phase difference between two component oscillations of equal frequency and, simultaneously, the amplitude of one of these component oscillations are each varied as a convenient trigonometric function of the modulating potential, the vector sum of these component oscillations will constitute an oscillation of constant amplitude but having a phase angle varying 1between 0 and 180 degrees in accordance with the amplitude of the modulating potential.

In particular, I utilize antiphasal or cophasal fractions of a main oscillation as the constant amplitude component oscillation while the component oscillation of Varying amplitude and phaseis directly derived from the main oscillation by means of a network comprising a susceptance and conductance connected either in parallel or in series to a thermionic tube inserted between the main oscillation source and the output circuit of `the phase modulation system and operating as an intermediate supply of constant current or constant voltage characteristics, respectively. I have found that by controlling the conductance in this network by means of the modulating potential so that the ratio` between conductance and susceptanceduring a complete cycle of modulation will reproduce substantially the trigonometric tangent function of 1r/2 times the relationship between the instantaneous value of said modulating potential and its maximum value, the phase angle of the derived component oscillation will vary linearly with the amplitude of the modulating,r potential, whereas its amplitude will Vary as` the sine or cosine of said phase angle. Hence, the-phase angle of the resultant vector sum oscillationwill vary between 0 and 180 degreesproportionally to the amplitude of the modulation, buty its amplitude will remain constant throughout the oomplete cycle of modulation. In a more concise form it can be stated that according to the invention the variable conductance is varied proportionally to the trigonometric tangent function of an angle proportional to the modulating potential.

It is therefore one of the main objects of the present invention to provide a phase modulation system wherein a linear relation between modulating potential and phase deviation of the modulated oscillation will be maintained over a range of A further object of the present invention is to provide a phase modulation system in which a phase variation of 180 is obtained in an `effective way by means of a circuit of simple layout;

The above and further features which I` believe to be characteristic of my invention are set forth in the appended claims; the invention itself, however, as to both its organization and method of operation will be best understood by reference to the following description taken in connection with the drawings in which I have indicated several circuit layouts whereby my 1nvention may be carried into effect.

In the drawings: v Fig. 1 is a wiring diagram of a phase modulation circuit according to the present invention. Fig. 1a illustrates a modification of the circuit of Fig. 1. p Y

Fig. 2 is a vector diagram given in order'to eX- plain the operation of the phase modulation c1rcuit shown in Fig. l. i Fig. 3 is another diagram relating to the operation of the phase modulation circuit shown in Fig. 1.

Fig. 4 illustrates a modication of thephase modulation circuit according to principles of the invention.

Fig. 5 shows ,another modification.

`Fig. 6 is a vvector diagram explanatory of the operation of the phase modulation circuit shown in Fig. 5, and finally Fig. 7 is a block diagram of a frequencymodulation transmitter including a phase modulator according to the present invention.

Similar or like elements or .parts .are :designated by the same reference characters and nu merals throughout the drawings.

Referring now -to Fig. 1 illustrating one embodiment of the Yphase modulation system .according to the present invention, it can be seen that an oscilla-tor l0 generating main oscillation has its goutput terminals .-II `r-and l2 coupled to cathode ,13 andcontrol grid IA, respectively, of a -therrnionic .pentode tube V1 the .anode `I5 `of which is connectedthrclgh a reactive .circuit consisting -of a vslightly fdetuned resonant circuit A formed of an 4 inductance i6 and .capacitance IFI, to the posi-tive vpole 1.8 o f `a 'direct .current supply 1.9L Screen grid 2,0 `of pentode V1 is connected to a tap `on directcurrentfsupply 4l 9 .the negative pole-.2.4i `'of which .is connected lto .ground potential together `with cathode .1.3 `,of tube V1 and terminal Il roimain oscillator l0,

Anode 1.5 ,of tube V1.and the corresponding end of vresonant circ-uitA arecoupled to anode 22 of a .triode tube V having its cathode 23 connected to nground potential, while its control circuit comprisme' 1COr1t1Dlfgiid 24 is .coupled to ,output terminals-2.5 and `2610i a modulator 21 generating a modulating potentialSlconveniently-derived from the .intelligence inaccordance with the exact nature .of the'wave to be radiated, i. `e. modulating potentials Abei-ng proportional `to the .intelligence or to the .time integral of the intelligence depending `on whether `a phase .or a frequency modulated wave .is to Vbe transmitted. The intelligence is considered in this particular use to be a signal voltage .the mathematical .expression of which as afunction of .time is stt) Yso that the .time integral of .the intelligence is represented by a quantityvvliich .is .derived .from .-the Vi,n-telligence shi) byan .integrating device well known -in the art the mathematical expression of which is Kfstt) dt.

been precisely indicated since it is immaterial and does not alter the operation of the circuit.

Thus, by means of V1 acting as a :source of constant current coupled to a susceptance B and conductance G connectedy in parallel, main oscillation e is directly transformed into component os- Y. .cillation W having a phase difference angle p Consideringresonant circuit A .and triode V as susceptance B and conductance G, respectively.,

connected .in'pa'rallel toa" source of constant current represented by .pentode V.; ige. that pentode .has .a :suciently .high .internal resistance Aand is ,capable of maintaining the current .supplied toznetwoik A independently'cf the load resistance presentedbythe latter, it will be understood that component oscillation W, developed between terminal .-28 (coupled to anode 22 of .triode v) and ground, .can be expressed in .terms of said susceptanceB ,and conductance G as follows: A

W=E.'cos cp cos (wt-HJ) .where H3196, component Voscillation -W may be represented 'byvector 219 having its Yphase shifted 90+@ f pn the net ampliiicaton of pentode 'V1 .h3/S '11@1? i equal to the arctang of the ratio between conductance G of triode .tube V and susceptance B of resonant circuit A, the amplitude of W being also a trigonometric function of said phase difference angle c.

' Ihave now found that by vectorially combining component .oscillation W with another component oscillation e'=0.5E cos ot of constant amplitude andfphase, an .output-oscillation of constant .amplitude 0.5L' .but `having a phase angle .egual vto two :times phase difference angle p will be obtained, so that .a variation of phase dilerence .angle p of component oscillation W from zero `to :.415" will cause `phase angle of output yoscillation 4tcwvary from zero to i90?, as is evident fromthe aforementioned trigonometric formulae and as will be explained hereinafter with .reference to the vector .diagram andA curves shownfin Figs. 2 and 3 respectively.

.Aswa-lready explained hereinabove, the tangent ofephase difference .angle ip is equal 4by denition to the .ratio of lconductance lG and susceptance B, so `that by varying the conductance of triode tube AV in accordance w'iththe amplitude of modulating potential S, a variation `of phase difference angle o, andfhence va corresponding variation of phase angle ,gb of zout-put oscillation U will be obtained. of Fig. 1 the operating conditions of triode V are so arranged that the relation of its internal conductance vvG with respect to control voltage eg c an be represented in Fig. 3 by curve 3|, which, giving in 4fact the ratio .of Gr to B, reproduces the tangent function between 0 `and'90 degrees, control voltage eg 'being proportional to the amplitudefof modulating potential S visualized by curve 32 in Ethesamegure.

In the fabsence `of .modulation a potentials@ equal to the voltage of ,the .C-battery 33 '(Fig. l) is present at control vgrid .24 of triode V, the circuit parameters .of the phase modulation circuit accordi-ng `to the present-invention being adjust-ad so that in due absence of modulation,` conductance {ST-gef triode V is equal'to susceptance B of parallel resonant circuit A. The above operating condition is representedin the vector diagram of Eig. 2 vby vector Vall which corresponds to output oscilflation 'in the absence of modulation and 'which represents the sum vof vectors 35 and 35' representing component oscillations e and W, respectively.

yDuring a complete cycle of modulation, the amplitude vof ,modulating potential S may vary about .its mean value So between the maximum negative and positive values Smm `and Smsx, respectivelv, so that in view ,of thetangent conguration vof Fig. 3, the ratio between G and B will vary as illustrated by curve 3l shown'in Fig. 3.

Hence, during ;a complete cycle of modulation, vector centered on point 3l' located atthe end `0i" vector `3e, will oscillate about line 38 between .a maximum negative ang-le 'o' of 45 and a maximum'positive angle o of +45, its amplitude simultaneously varying between zero and a value equal to the amplitude of vector Bil.

The end .of vector 36 will therefore describe a 4In the phase modulation system semi-circle 39 during a complete cycle of modulation, and vector 34, representing phase modulated output oscillation U, will oscillate about line 40 corresponding to the output oscillation in absence of modulation as indicated by the arrow in the diagram of Fig. 2, its phase angle fp varying between the extreme values of i90 degrees. Since vector` 34 represents the radius of semicircle 39, the amplitude of output oscillation U remains constant throughout the whole phase modulation range which covers a total of 180J and in which phaseangle ip is proportional to the amplitude of modulating potential S.

As can be seen in the circuit diagram shown in Fig. 1, the vectorial addition of component oscillation W and e is carried out in a thermionic mixer tube V2, the control grids 4l and 42 of which constitute the inputs for component oscillations W and e', respectively. Control grid 4| is directly connected to terminal 28 of the parallel network, while control grid 42 is coupled to the secondary winding 43 of a transformer T, the primary winding 44 of which is coupled to output terminals Il and I2 of main oscillator l0. Transformer T, is designed so that component oscillation e applied to control grid 42 is of an amplitude equal to a convenient fraction of the amplitude of main oscillation e but has its phase rotated -90 with respect to the phase of main oscillation e. Said fraction is adjusted in accordl ance with the relation of the slopes of mixer tube V2 with respect to control grids 4| and 42, so that the voltage fraction developed across load impedance Z of Vz'and corresponding to component oscillation e Will have half the amplitude of the voltage fraction corresponding to component oscillation W. Load impedanceV Z is formed of a resonant circuit tuned to the frequency of main oscillation e, so that the voltage lbetween terminals 44 and 45 of said load impedance Z will represent the vector sum of component oscillation W and e having a correct amplitude ratio as shown in the vector diagram of Fig. 2. The amplitude of output oscillation U will be constant while its phase angle will vary in accordance with the amplitude of modulating potential S, which in turn controls the Variable conductance G connected in parallel with susceptance B and constituted by triode tube V.

A5 explained hereinbefore, in the phase modulation system according to the present invention, a phase variation of 180 degrees can be easily obtained by varying the phase of component oscillation W over a range of 90 only. Theoretically, such phase modulation requires a variai tion of conductance G between zero and infinity, but it will be understood that for all practical purposes it will be quite suncient to vary conductance G between zero and a maximum value equal to at least ten times the value of susceptance B. The dotted portions` 3i of curve 3i shown in Fig. 3 have been drawnaccording to the above limitations Which can be easily overcome by a judicious choice of a suitable valve type for triode V and by conveniently adjusting the operating conditions of the tube.

Although in the circuit diagram shown in Fig. 1 'susceptance B is f-ormed by parallel resonant circuit A, it should be noted that a capacitance alone can also be used for this purpose if the frequency of main oscillation e is below 1 rnc/s., since for is higher than 1 mc./s. the use of resonant circuit for 'susceptance B becomes necessary, since by tuning .the resonant circuit to either side of resonance, the absolute magnitude of susceptance B can be easily adjusted to any desired value.

The above modification is illustrated in the circuit shown in Fig. 1a, where it is seen that the anodes of thermionic tubes V1 and V are connected to the positive pole I8 of D. C. source I9 through a common choke coil I6', a capacitor Il constituting the susceptance B being connected in parallel with variable conductance tube V. In other respects the phase modulator shown in Fig. la is exactly similar to that of Fig. 1.

Fig. 4 illustrates a circuit arrangement similar to that of Fig. 1, but differing therefrom in that variable conductance G is formed as the sum of the cathode conductance Gc and the platecathode transconductance Gm of a thermionic pentode tube V connected as a cathode follower between parallel resonant circuit A and thermionic mixer tube V2. Modulating potential S is applied to control grid 41 of pentode V', so that total conductance G connected in parallel across resonant circuit A, can be varied between a fixed minimum value determined by cathode resistance 46 and a maximum value depending upon the operating potentials of the tube electrodes.

The utilization for Variable conductanceG, of pentodes connected as cathode followers is particularly advantageous since the Gm-eg characteristic of variable mu pentodes can be adjusted to perfectly reproduce the tangent function between Zero and 90 degrees.

In the embodiment of the present invention shown in Figs. 1 and 4, phase modulated output oscillation U is obtained by vectorially combining component oscillation e' .of constant amplitude and phase with component oscillation W of variable phase and amplitude derived from main oscillation e by means of a network comprising pentode tube V1, susceptance B and coni ductance G connected in parallel. Fig..5 illusthese relatively low frequencies the relation 1:10

trates a modification of the phase modulation system according to the present invention, differing from the circuits of Figs. 1 and 4 in that output oscillation Uf. is obtained by vectorially combining a component oscillation e" of constant amplitude cophasally derived from main j oscillation e with another component oscillation W' of varying phase and amplitude derived from main oscillation e by means of a network constituted of a triode tube V'i acting as a source of constant voltage and connected across a resonant circuit A having a reactance L and connected in series with a triode tube V" of an internal resistance R.

As can be seen in the circuit diagram shown in Fig. 5, output terminals Il'` and l2" of output oscillator lil generating main oscillation e=Ea sin wt are connected to cathode 48 and control grid 49, respectively, of triode tube V 1 the anode 5,0 of which is connected to one end of parallel resonant circuit A constituted by an inductance I6 and capacitance l1. The other end of resonant circuit A is connected to anode 22' of triode tube V", the junction point 5| between tube V and resonant circuit A being connected to the positive pole I8' of a direct current supply i9 through choke coil 52. The negative pole 20 of direct current supply I9 is connected to ground together With terminal l I of main oscillator l0' and cathodes 48 and 23 of triodes Vi and V", respectively.

Modulating potential ,S generated in modulator 2l is applied to control grid 24 vof tube V'f to .Vary the internal resistance R of thistube in accordance with the amplitude variations of modulating potential S as will be explained hereinafter, so that a component oscillation -W of .varying phase and amplitude will be obtained between junction point 5| and ground.

In fact, considering triode tube Vi as a source of constant voltage i. e. assuming that triode V1 has a suiiiciently low internal resistance and is capable of maintaining the voltage applied to network A independently of the load represented by the latter, and assuming that resonant circuit A. is tuned so as ,to presenta reactance L at the frequency of main oscillation e, it will be understood that component oscillation W is substantially equal to E sin e cos iet-ho), .where Hence, by vectorially combining component oscillation W' with 4component oscillation 5:95 E sin wt), an output oscillation U'=0.5 E sin (wt-lap) Willbe .obtained .Where vphase angle 30:23u. Since phase angle t of .output oscillation U' can be modulated by varying internal resistance R of triode V" in such a way that the ratio of re- Sistane R. i/ meterme L during a Complete cycle of modulation reproduces a tangent function between zero and90 degrees. N

l Actually, the operating conditions of triode tube V'" are similar to theseof iriode tube. V irl the circuit shown `in Figs. 1 and 4. Consequently, in the vector diagram' shown in Fig. 6, vector 53 .representing cut-put oscillation U' in the absence of modulation is equal to the sum of vectors 54 .and 5 5 corresponding .to component oscillations c and W', respectively.

`As can be seen in the diagram, vector l54 is in phase with vector A56 representing main oscillation e`.-=E0 sin wt, the relation between the scalar values 4of 'vectors 5.4 and 55 corresponding to the amplitude relations ,of the respective oscillations. During a complete cycle of modulation, Vector 55 .corresponding to the instantaneous value of component `oscillation W' will Voscillate about line 51 while beingv centered on point 58 located at the endfof Vector 54. The maximum phase diiierencc angle c between line 51 and vector V55 is equal to 145, While the amplitude of vector 55 Varies between a Value equal to the amplitude of main oscillation e and zero.

Hence, during modulation vector 53 will 0scillate i90aboutline59 and describing with its end semi-circle 60, so that its amplitude and consequently the amplitude of outputr oscillation U' Will remain constant over the entire range oi' variations of phase angle w.

Component oscillation W is applied to control grid 4| of a thermionic mixer tube Vz, while component oscillation e" is derived from main oscillation e by means of alpotentiometer P connected to oscillator terminals Il' and I2', controlgrid 42 of thermionic mixer tube V2 being connected to the junction point of resistances 5l and 62 constituting potentiometer P.

Resistances 6I and 62 are designed so that the vol-tage yfraction corresponding t0 e and developed across load impedance Z yof mixer tube Vz is equal to half the amplitude-of the voltage fraction .corresponding to component `oscillation W', .so that phase VAmodulated oscillation U pears asthe vector sum of both component .oscillations W and e between output termina-ls 44 and 45' `connected to said load impedance Z which is constituted by a resonant circuit tuned to the frequency of main oscillation e.

It will be evident that in the phase modular tion circuit shown .in Fig. 5, triode tube V5 acting as a Variable resistance R .can be replaced by fa pentode connected `as cathode follower assllpilul in Fig. .Il without affecting the correct operation of the system. Similarly, the vectorial addition of component oscillations e', W vor ,e, W may also be carried out by `:applying .both oscillations to a common control grid of a therrnionic tube which would develop .the phase modulated output oscillation in its Vplate circuit.V It should be noted. however, that a suitable thermionic separating stage should be inserted .in the connection .coli-v piing main oscillator 4Il) to the control grid ,o .f the mixer ltube in order to prevent the genera,- tion of parasitic oscillations in the, circuit.

Fig. '7 illustrates the utilization of one .of .the phase modulation .circuits according to the present invention in a frequency `modulation transniitter. As can :be seen in the drawings, output terminals 4t'. and 4,5 of the phase modulator designated by the general reference numeral S'Sla're coupled to a frequency multiplier stage 64 connected in turn to a power ampllier stage .5,5 pro.- vided with an antenna 66, so that the frequency of the radiated carrier `wave will vary in accordance with modulating potential S generated in modulator 21.

As stated above, it should be understood that the modulating potentials is proportional tothe e ments of my invention, itfwill of course, be vunderstood that I do not wish to be limited-thereto since many modications may be made without departing from the spirit .and scope of my invention as dened in the following claims.

I claim: Y'

l. A system for modulating the phase .of an electrical oscillation in accordance with a modulating potential, which comprises a source of main oscillations coupled through a means of constant output current characteristics to va network constituted by a suSCSptance and a vari-v able conductance connected in parallel, Ymeans to vary said conductance proportionally to .the tangent of an angle proportional to the amplirude of said modulating potentiai 4to produce@ rst component'oscillation having a phase ingle varying as the ratio of said conductance t0 said susceptance and an amplitude ,Varying proportionally to the cosine of `the said phase angle, means to derive a second component oscillation of constant amplitude and in lagging phase quadrature with respect to said main .oscillation, and means t0 Vectorially combine said @rst and second component oscillations'to .produce a resultant oscilation of constant amplitude hay'- .ing a phase angle linearly proportional 4to the amplitude of said modulating potential.

2. In a system for modulating the phase angle of an electrical oscillation, a .thermioni-c .pentode tube having a control electrode, a cathode and an anode, a source of main oscillations .connected between said cathode and said control electrode, a network comprising a susceptance circuit ele- Vment and a variable conductance connected in parallel, said variable conductance being constituted by the anode-cathode conductance of a thermionic triode tube having a control electrode, a cathode and an anode, said triode tube having a response characteristic with respect to the control electrode voltage at which the ratio of the triode conductance to the said circuit susceptance is substantiallly proportional .to the tangent function from zero to 1r/2, means to connect one end of said susceptance circuit and the anode of said triode tube to the anode of said pentode, means to connect a source of modulating potential to the control electrode of said triode tube to produce a rst component oscillation having a phase angle varying in accordance with the ratio between said anode-cathode conductance and .the susceptance of said susceptance circuit and an amplitude varying proportionally to the cosine of the said phase angle, means to derive a second component oscillation of constant amplitude and in lagging phase quadrature with respect to said main oscillations, and means to vectorially combine said rst and second component oscillations to produce a resultant oscillation of constant amplitude having a phase angle linearly proportional to the amplitude of said modulating potential.

3. In a system for modulating the phase angle of an electrical oscillation, a thermionic pentode tube having -a control electrode, a cathode and an anode, a source of a main oscillation connect-5 .ed between said cathode and said control electrode, a network comprising a susceptance circuit constituted by parallel resonant circuit elements and a Variable conductance connected in parallel, said variable conductance being constituted by the anode-cathode conductance of a thermionic triode tube having a control electrode, a cathode and an anode and having a response characteristic with respect to the control electrode voltage at which the ratio of the triode conductance to the said circuit susceptance is Vsubstantially proportional to the tangent function from zero to 1r/2, means to connect one end of said parallel resonant susceptance circuit and andthe anode of said triode tube to the anode of said pentode, means to connect a source of modulating potential to .the control electrode of said triode tube rto produce a rst component oscillation having a phase angle `varying as the ratio between said anode-cathode conductance and the susceptance of said resonant circuit and an amplitude varying proportionally to the cosine of the said phase angle, a transformer having a primary `and an unloaded secondary winding, means to connect said primary winding to said main oscillation source to produce across said secondary winding a second component oscillation of constant amplitude and in lagging phase quadrature with respect to said main oscillation, a thermionic mixer tube having .two control electrodes and an anode loaded by a circuit .tuned to the frequency of said main oscillation, and means to connect the control electrodes of said mixer tube to said network and to said unloaded secondary winding, respectively, to produce in said load circuit a resultant oscillation of constant amplitude equal to the vector sum of said rst and second component oscillations and having a phase angle linearly proportional to the amplitude of said modulating potential.

4. A phase modulator system according to claim 3,V wherein the maximum amplitude of Vsaid rst component oscillation in said load circuit is equal to two times the amplitude of said second component oscillation in the same load circuit.

5. In a system for modulating the phase angle of an electrical oscillation, a thermionic' pentode tube having a control electrode, a cathode and an anode, a source of a main oscillation connected between said cathode and said control electrode, a network comprising a susceptance circuit -constituted by parallel resonant circuit elements and a variable conductance connected in parallel, said variable conductance being con- VstitutedV by a thermionic pentode .tube having a control electrode, a cathode and an anode and `a resistance connected in series with said cathode and anode and connected in shunt with said susceptance circuit, said second pentode tube having a response characteristic with respect .tothe control electrode Voltage at which the ratio of the said conductance to the said circuit susceptance is substantially proportional tothe tangent function from zero to 1r/2, means to connect said susceptance circuit and said conductance to the anode of said rst pentode tube, means to connect a source of modulating potential to the control electrode of said second pentode to produce `a rst component oscillation having a phase angle varying proportionally to the ratio between said conductance and the susceptance of said network and an amplitude varying proportionally to the cosine oi the said phase angle, means to .de-

rive a second Acomponent oscillation of constant amplitude and in lagging phase quadrature with respect to saidW main oscillation, and means .to

. vectorially combine said rst and second compo- Vnent oscillations to produce aresultant oscillation of constant amplitude having a phase angle linearly proportional to the amplitude of said modulating potential. l

`6; A system for modulating the phase of-an 'electrical oscillation in accordance with a modulating potential, which comprises a source `of `a main oscillation coupled through a means of constant output voltage characteristics to :a network vconsisting of a reactance and/a variable resistance connected in series, means to vary said resistance proportional to thetangent of an angle proportional to the amplitude of said modulating potential to produce a first component oscillation havinga phase angle varying in accordance with theiratio Vbetween said resistance and said reactance and an amplitude varying proportionally to the sine of the said phase angle,` means to cophasally derive a second componentoscillation of constant amplitude from said main oscillation, and means to vectorially combine said first and second component oscillations to produce a resultant oscillation of constant amplitude having a phase angle linearly proportional to the amplitude of said modulating potential.

y'7. In a system for modulating the phase angle of an electrical oscillation, a thermionic triode tube having a control electrode, a cathode and an anode, a source of a main oscillation connected between said cathode and said control electrode, a network comprising a reactance circuit constituted by parallel resonant circuit elements and a variable resistance connected in series, said Variable resistance being constituted by the internal resistance of a second thermionic triode tube having a control electrode, a cathode and an anode, said second triode tube having a response char- 11 acteristic vvith respect to the control electrode volta'geat which the ratio'lof. the triode internal resistance to said circuit reactance is' substantially proportional t the tangent function fro o to 1r/2, means to connect the end of said reso `nt circuit remote from the anode of said .second triode to the anode ofV the' first triode tube means to connect a source of modulatingr potentialto the control electrode of said second triode tube 4to producea ilrst component oscillation having" a phase angle varying proportional to the `ratio between said internal resistance and the reactance of the parallel resonant circuit elementsan'd anamplitude varying proportionally to the sine of the said phase angle, meansnto copliasally: derive a second component oscillation of constant ain#- plitude from said main oscillation and means to vt'af'ztoifi'ally combine said r'st and second component oscillations to produce a resultant `oscillation of constant amplitude having a phase angle linearly proportional to the amplitude of said modulating potential. I t y u 8`. vIn a system for ymodulating` the phase angle ofA an electrical oscillation,` a therinioni'c vtriode tube havingr a control electrode,v a cathode `andan anode, a', source of a main oscillation connected between said cathode and said control electrode, avnctworl comprising aV reactance circuitconstitiited py parallel resonant circuit element-s and a', variable resistance connected in series, said variable resistance being constituted by the internal resistance of a l:second tlfiel-mlonic triod tube having 'a control electrode; a cathode and an anode, second `turiodewhailingl a response characteristic with respectto the control electrode @tassa which the ratio of ,the time parte resistanceuto the said reactance is `substarl to ',t'lio frequency of tiro main oscillation, and

' means Yto connect the control electrodesof said Zarate ,1f/amines ,to conne@ ,thtsiid if ,Seid fes'- onant circuit remote from the anode of saidtsec.-

` ond triode to the anode of vthe triode tube,

and an, amplitude varyingproportionally to the sineV of--tlle said phase angle, tWo resistances con- -nectedin series and coupled to said mainoscillationl source togproduce across one of said resistancesa second component oscillation of constant amplitude iii-phase Withsaid main oscillation, a

thermionic lnixer tube having two control elec;- trodes and an anode loaded by a circuit tuned mixer tube to' the anode oimsai-d second tri'de tube and to the' ignoti-ori point; between said tjosistances, respectively, toy produce wirr said lad lcircuit al resultanti oscillation of v(constajn't,4 amiplitude equal to the vector sum` of4 said rstvfan'd second component oscillations and having' a phase angle linearly proportional to' the amplitude of said modulating potential. I l, i K e 9. A system for modulating lthe kphase angle: of

an electrical oscillation in accordance Witha AmodV ulating' potential, Which comprises' Va sour main' oscillation, a network comprising vat ysuse 'tance and a variable conductance coupled to said source, means energized by said modulating p`otential to vary said conductance Vprop orti nal to the trigonometrictangent function fromhnero to 1r/2 of an angle proportional to the amplitude of said modulating potential to produce a first rfip'onent oscillation having a phase angle as the ratio ofv said conductancet'o saidsusceptance and an amplitude varying as a trigonometric function oi said phase angle, means to derive a second component oscillation of constant amplitodo and phase with respottto said mais oscillation, and means to vctoriallyconirbine said 'r'st andsecor'd component oscillations to produce a resultant osclllationof constant amplitude havlng a phase ansia linearly proportional to the amplitudeofi` said in dillatirlx;y potential. A

A10. A system for modulatin the phase of ani electrical oscillation! in accordance ivithav rnodimating potential,- whith comprises a 'souroejof main oscillations oupled'through l'ai fri'eans of constantoutput current characteristicsto a network constituted by afcapacijtance'and a variable coil'- 'ductance element connected in parallel; means' to vary saids conductance H proportionally to the trigonomtrie tangent finit'tion from onto: 2 lor an `aosta proportional to saidfnioddlatin tetialto produ4 rstcomponentosoilla A n having 'a phase "nele varying jas tnoratio of t" e conductance of said element to tnosusoe .ce dfv sli' capfiitsiic 'and ,auf fiiin'lilitirtv Varying proportionally to the cosine of the) said phase angle,` means to derive Va. second A coni'ponent o s'cil'- lation of constant anplit'ud'eV and i'n lag'ging phase on'adtatiire with' ospe'ot to said mais osoilratiorr,

andmmeans to vectorially combine saidnlst andL l second component oscillations to' produce' 'a y sultantoscillation oftoo'ostant amplitude hating a piiassaoglo linearly l.propo'iftioiial to the amfplitude of said modulatin potei/itial.V 'y d EDOUARD LABEL 

